Is a high heart rate when exercising normal?

There are lots of things that can increase your heart rate, such as drinking caffeinated drinks or alcohol, or even having an heated argument! The heart should match the beat rate to the demands of your body, so that the right amount of blood gets pumped. If you pump too little blood your tissues become starved, but if you pump too much you're wasting energy. There are some medical conditions that can make the heart pump too fast, but usually they don't cause the heart to go fast all the time.It's hard to say what's a 'normal' heart rate, as diet and level of fitness can really make a big difference.